In swamps, wetlands, marshes and shallow bays, geophones encased in special geophone housings or marsh cases are used in seismic exploration surveys. Marsh cases in general consist of an upper and lower body with the geophone transducer sealed within. The lower end usually houses the geophone transducer and has a tapered end cone or spike to facilitate the insertion of the element into the muddy surface bottom. The upper end of the case has an electrical cable entry area through which some form of cable seal is accomplished. The conductors in the electrical cable are attached to the internally housed geophone transducer and conduct the electrical signals to a recording device through interconnecting cables. The cable entry area must be sealed to prevent moisture from entering within. The upper end of the housing or marsh case is designed to be accepted by a planting attachment on the end of a pole so that the marsh case can firmly be implanted into the surface bottom.
After the survey operations have been completed at a given location, the geophone housing is recovered beneath the muddy surface bottom by pulling on the cable. For prior art, see U.S. Pat. No. 3,931,453 and U.S. Pat. No. 4,470,134. Either of these cases, mentioned in the above patents, do not exclude moisture if the electrical cable outer jacket is cut though, and into the internal conductor's insulation. Water can migrate down the conductors and penetrate into the cavity housing the geophone transducer element causing electrical leakage, or possible short circuit conditions. U.S. Pat. No. 5,014,813 provides a waterproof housing, but is non-repairable if damage occurs to the geophone transducer for any reason. Nor does this design allow for the replacement of the transducer when desired.
This invention provides the latest improvements of a repairable marsh case design or geophone housing that provides a rugged structure which is not subject to leakage during harsh field usage or handling.